1. Field of the Invention
The present invention relates to a liquid crystal display device, and particularly, to an in-plane switching mode liquid crystal display device and method of fabricating the same.
2. Description of the Related Art
In general, twisted nematic mode liquid crystal display (LCD) devices commonly used as flat panel display devices have advantages of high image quality and lower power consumption. However, twisted nematic mode LCD devices have disadvantages, such as narrow viewing angles, due to refractive anisotropy of liquid crystal molecules being oriented in parallel with a substrate along a nearly vertical direction to the substrate when the voltage is supplied to the liquid crystal display panel. Accordingly, in-plane switching mode LCD devices have been developed that can solve the viewing angle problems by orienting the liquid crystal molecules to be parallel with the substrate.
FIG. 1A is a plan view of a unit pixel of an in-plane switching mode LCD according to the related art, and FIG. 1B is a cross sectional view along I-I′ of FIG. 1A according to the related art. In FIG. 1A, a gate line 1 and a data line 3 are arranged along transverse and longitudinal directions, respectively, on a transparent first substrate 10 (in FIG. 1B) to define a pixel area. In actuality, there are an n-number of n×m pixels by crossings of an n-number of gate lines 1 and an m-number of data lines 3 formed on the transparent first substrate 10. In addition, a thin film transistor 9 includes a gate electrode 1a, a semiconductor layer 5, and source and drain electrodes 2a and 2b disposed within the pixel area, wherein the gate electrode 1a is connected to the gate line 1, the source electrode 2a is connected to the data line 3, and the drain electrode 2b is connected to a pixel electrode 7. Moreover, a gate insulating layer 8 is formed on an entire surface of the transparent first substrate 10.
A common line 4 is arranged to be parallel with the gate line 1 within the pixel area, and at least a pair of common and pixel electrodes 6 and 7 for switching the liquid crystal molecules are arranged to be parallel with the data line 3. The common electrode 6 is simultaneously formed with the gate line 1 and is connected to the common line 4, whereas the pixel electrode 7 is simultaneously formed with the source and drain electrodes 2a and 2b and is connected to the drain electrode 2b of the thin film transistor 9.
In FIG. 1B, a passivation layer 11 and a first alignment layer 12a are formed along an entire surface of the transparent first substrate 10 including the source and drain electrodes 2a and 2b. It is desirable that the common electrode 6 is formed along an outer portion of the pixel area in order to shield any lateral electric fields generated between the pixel electrode 7 and the data line 3 formed along the outer portion of the pixel area. In addition, a pixel electrode line 14 is formed to overlap the common line 4 and is connected to the pixel electrode 7, thereby forming a storage capacitor with the gate insulating layer 8 therebetween.
A black matrix 21, which prevents light from leaking to the thin film transistor 9, the gate line 1, the data line 3, and a color filter 23 are formed on a second substrate 20, and a second alignment layer 12b is formed thereon. In addition, a liquid crystal layer 13 is formed between the first and second substrates 10 and 20. However, the in-plane switching mode LCD device of FIGS. 1A and 1B has a low aperture ratio since the common electrode 6 and the pixel electrode 7 are formed of opaque metals within the pixel area.